If it is just css customizations, use this plugin:
http://wordpress.org/extend/plugins/safecss/
It’s what wp.com uses for their css upgrade.
If you have to edit the php, make a copy of the theme with a new name on the theme folder and in style.css.
If it is just css customizations, use this plugin:
http://wordpress.org/extend/plugins/safecss/
It’s what wp.com uses for their css upgrade.
If you have to edit the php, make a copy of the theme with a new name on the theme folder and in style.css.